Nice work Lee, dreads look good! The silicone (I'm guessing it's a silicone mold?) should last about 2 sets of dreads before it starts to lose its nonstick properties. You can prolong that with release agents of course.
Also as far as soft/stiffer dreads, it was probably the mix ration you used on the foam. On both the foams I've tried, more Part A to the mix has resulted in a softer, more flexible foam. I recommend you experiment with it. I measure everything out with a scale too. Even the foam that says to measure by volume...much better to do it by weight.